Petrological and Geochemical Characterization of Miocene Tipam Sandstone in Parts of Cachar Fold Belt, Northeast India

Abstract

Miocene Tipam Sandstone Formation in parts of Cachar Fold Belt, Northeast India has been studied using petrographic and geochemical attributes to investigate the composition, paleoweathering, tectonic setting, and source rock characteristics. It comprises of coarse to medium grained false-bedded multistoried ferruginous sandstone and variegated sandy clay. Petrographically, these sandstones belong to sub-lithic and lithic arenite varieties possessing an average recalculated modal composition of Q₆₇F₁₃R₂₀. Geochemically, Tipam sandstones have high SiO₂, more Na₂O than K₂O, and relatively low Fe₂O₃, MgO, MnO content in accordance with the modal composition. Weathering indices like CIA, CIW, PIA and ICV suggest derivation of sediments from low to moderately weathered source terrain bearing plagioclase feldspar in the range of An₁₀ – An₅₅ comparable to granodiorite and granite composition. Dominantly a passive margin setup with high degree of sediment recycling has been envisaged during the deposition of Tipam Sandstone Formation.